246 THE VOYAGE OF H.M.S. CHALLENGER. 



1. Actinal spines of the adambulacral armature very long, 



equal, delicate, needle-like, and slightly curved. 

 Pedicellarise very small, resembling clavate papillae. 

 Infero-marginal plates with three spines, the lateral 

 and median one long and equal, the inner one 

 rather shorter. Rays long and gradually tapering. 

 Paxillae with no robust central spinelet, but some- 

 times two or three of the same size as the encircling 

 series africana. 



2. Actinal spines of the adambulacral armature, short, 



cylindrical, equal, delicate. Pedicellarise very few, 

 small, papilliform. Infero-marginal plates with 

 three spines, the lateral and median one long and 

 equal, the inner one smaller. Pays short and 

 abruptly tapering. Paxillae with a short robust 

 central spinelet. ....... sarsii. 



b. Adambulacral armature not forming a single transverse series continuous 

 with the spines on the infero-marginal plates. 

 a. Paxillae at the sides of the rays with a slightly quadrate character. 

 A large pedicellaria accompanies the outer spinelet on the 

 actinal surface of the adambulacral plates ; the pedicellaria and 

 spine standing as a pair side by side behind the single median 

 and furrow spines ........ forfieifer. 



Chorology of the Genus Luidia. 

 a. Geographical distribution : — 



Atlantic : Ten species between the parallels of 65° N. and 40° S. 



On the eastern side : Luidia sarsii, in the northern area, from 

 the coast of Norway to the British Islands. Luidia ciliaris, from 

 the Faeroe Channel in the North to the Mediterranean. *Luidia 

 africana, off the coast of Morocco and extending to the extreme 

 southern point of Africa. Luidia senegalensis, off the west coast of 

 Africa, and extending to the Antilles and Brazil. 



On the western side : * Luidia clathrata, extending from North 

 Carolina, through the West Indian area, as far south as Brazil (Rio 

 Janeiro). Luidia elegans, off North Carolina and in the West 

 Indian area. Luidia variegata, in the Gulf of Mexico, off the mouth 

 of the Mississippi. Luidia convexiuscula, Luidia barbadensis, and 

 *Luidia alternata, in the West Indian area, the last mentioned 

 extending northward to the coast of Florida and southward to Bahia. 

 Indian Ocean : Three species between the parallels of 30° N. and 10° S. 



Luidia savignyi, in the Bed Sea and off the east coast of Africa. 

 Luidia maculata, in the Indian Ocean from the coast of Africa in 



